Representative samples of fourth- and eighth-grade public school students from 21 urban districts participated in the 2011 National Assessment of Educational Progress (NAEP) in mathematics. Eighteen of the districts participating in the 2011 NAEP Trial Urban District Assessment (TUDA) participated in earlier assessment years, while three districts participated for the first time in 2011. Between 1,000 and 2,700 students in each district were assessed at grades 4 and 8. Findings include: (1) Scores higher than in 2009 for four districts at grade 4 and six districts at grade 8. At grade 4, average mathematics scores were higher in 2011 than in 2009 for public school students in the nation, large cities, and 4 of the 18 urban districts that participated in both years (figure A). At grade 8, average mathematics scores were higher in 2011 than in 2009 for public school students in the nation, large cities, and 6 of the 18 urban districts that participated in both years; (2) Among the 21 urban districts that participated in the 2011 mathematics assessment, scores for both fourth- and eighth-graders in 6 districts were higher than the scores for public school students attending schools in large cities (i.e., cities with populations of 250,000 or more) overall. Fourth- and eighth-graders in 10 districts scored lower than their peers in large cities; and (3) Compared to large cities, scores for lower-income students are higher in eight districts at grade 4 and five districts at grade 8. At grade 4, average scores for both higher- and lower-income students in Austin, Charlotte, and Hillsborough County were higher than the scores for their peers in large cities (figure B). At grade 8, average scores for both higher- and lower-income students in Austin and Boston were higher than the scores for their peers in large cities. (Contains 21 figures and 25 tables.)